9O Smith's Fire.
for the rest of the day, and has many advantages, as will be seen
Fig- 95 represents an ordinary smith's hearth, built up partly o:
brick and partly of iron, a is the blast nozzle, which need noi
now be surrounded by water, because the fire will never be nearei
to it than the position marked b, and so no caking can happen,
In building the ' stock' a loose brick is first taken out at c, and a
bar passed through and inserted in the tuyere. The coal is now
damped by sprinkling water upon it with a wisp of straw, and is
built up into the form shown, the ridge d being neatly flatted
down, by using the back of the shovel. Beginning at the tuyere
and advancing frontwards the * stock J is finished round the piece
of wood <?, which is called the t stock block.' We may now
remove both bar and block, and make the fire in the space e.
The iron to be heated is placed in this space and covered up with
loose coal, which is always brought from the front end <:, so
that the stock gradually burns away to the end b by the close of
the day. The advantages of ' stock' working are these: (i) we
need no water tuyere nor consequent attention to water supply;
(2) the bar to be heated is only acted on by the fire to the length
required (whereas ' open' working has a tendency to heat it to a
.greater extent); and the method is generally more economical.
The Blast.—Air is constantly supplied to the fire, when
working, by means either of bellows, fan, or blower, one of the
*|f! latter two being in use at an engineers' smithy, where all the'
fires are connected to one main blast pipe. Fig. 95A, Plate I.,
represents a fully equipped smithy, as designed by Messrs.
Handyside, and fitted with their hearths throughout The
iS main blast pipe is shewn by the dotted lines in plan.
Fig. 93 is a drawing of a Fan l^jr Sturtevant. There should
be a good large space left beyond the vanes, to allow the velocity
energy given to the air by them to be easily transformed into
pressure energy in the pipe, and so prevent waste by eddies.
Roots' Blower, as made by Messrs. Samuelson, of
Banbury, is shewn at Fig. 94. The air in this machine is
iff literally scraped out of the casing on the side A, by the revo-
/ ; lution of the two figures s s, in opposite directions, and is delivered,
at B, a fresh supply replacing the partial vacuum formed The
rollers, as the above figures are called, are compelled to work